1. Field of the Invention
The present invention relates a method for measuring the length and a relative moving speed of an object moving with respect to a point of observation from time sequence image data produced by using line scan cameras and the like, and a pattern recognition method and apparatus based on the resulting image data.
2. Description of the Related Art
An example of the method of measuring a speed of a moving object using a plurality of sensors is based on the use of two phototubes. In this method, two phototubes are placed apart in parallel, and the speed of the moving object is obtained from the timings of the object crossing the two phototubes in successive instances, and is widely used for speed measurements of cars and other moving objects.
On the other hand, the following references are examples of the method for determining the speed and length of a moving object from images. xe2x80x9cTraffic flow measurements using the double slit methodxe2x80x9d (reference 1, Road Traffic and Automobiles, The Institute of Electrical Engineers of Japan, Vol. RTA94-5, 1994) and xe2x80x9cTraffic flow measurements using the double slit cameraxe2x80x9d (reference 2, The Institute of Electronics Engineers of Japan, Vol.26, No.3, 1997). These methods are based on providing imaginary slits within the images recorded using a general purpose video-camera and obtaining spatial time images by linking the images between the slits. Two slits are placed in the images, so that the moving speed and the length of the object are measured by obtaining the time interval for the object to pass through the two slits.
However, in the above related art, there are problems outlined in the following.
When either the observation point or the vehicle moves along a determined track, and considering the topics for measuring relative speeds, the length of the object and recognizing the pattern of the moving object using the conventional phototubes, it is necessary to position the phototubes so that they surround the object. Also, because it is not possible to obtain images by this technique, it is not possible to know what type of object had passed between the sensors. Therefore, it is necessary to visually confirm the nature of the object.
In the meantime, according to conventional video images, because the two slit planes are not parallel, the depth of field must be fixed first, so that the distance of movement between the actual slits can be determined separately. Also, the general purpose video camera can only record at 30 frames/second, so that if the object is moving at high speeds, it is not possible to produce precision measurement of speed. Also, there is no known method of measuring the relative speed of an object using the images taken by placing a camera on another moving object.
It is an object of the present invention to solve the problems inherent in the conventional technology and provide a method for measuring speed and length of an object and a method of recognizing a shape pattern and to provide an apparatus for use therefor. The topic of the present invention to provide a technique of processing data simply when an observation point and an object are moving relative to the other to obtain a relative moving speed; when an observation point is stationary and an object is moving to obtain a relative moving speed and a length of the object; and a shape pattern recognition method in such cases.
According to the present invention, the object has been achieved in a method for processing image data to measure a relative speed of a target object moving along a given track relative to an observation point, comprising the steps of: obtaining time sequence image data recorded by synchronously operating a plurality of line image acquiring apparatuses, arranged transversely to the given track of the moving object, so as to record time sequence images appearing between two parallel line axes at a constant timing determined by a line scanning cycle; correlating framed images of the object in the time sequence image data by computing a similarity degree, and obtaining a moving time interval of the object, to move between the line image acquiring apparatuses, from correlated images according to the value of time displacement of the object and the line scanning cycle; and obtaining a relative speed of the object relative to the observation point according to the moving time interval and a distance separating the line image acquiring positions of the line image acquiring apparatuses.
Using the method presented above, line image acquiring apparatus is able to obtain clear images in a short interval time, and using the images thus obtained, a relative moving speed of the object can be measured.
Also, the object of the present invention has been achieved in a method for recognizing an object having a specific shape pattern that can be recognized as an image moving along a given track relative to an observation point, comprising the steps of: obtaining a relative moving speed of the object moving relative to the observation point according to the method recited above; matching a time scale of the time sequence image data and a time scale of a template for the specific shape pattern prepared beforehand by correcting respective time scales according to the relative moving speed; and computing a similarity degree between the time sequence image data and the template of the special shape pattern having a matched time scale, thereby detecting and recognizing the specific shape pattern in the time sequence image data.
Using the method described above, it becomes possible to readily recognize a pattern belonging to a moving object.
Also, the object of the present invention has been achieved in a method for measuring a length of an object from time sequence image data obtained at a stationary observation point by recording the object moving along a given track, comprising the steps of: obtaining a relative moving speed of the object moving relative to the observation point according to the method recited above; detecting a starting point and an ending point of the object in each time sequence image data by evaluating whether or not a difference value between a framed image and a time sequence background image data prepared beforehand, exceeds a threshold value; and obtaining a recording time interval between the starting point and the ending point according to the line scanning cycle, and computing the length of the object from the recording time interval and the moving speed of the object.
Using the method described above, it is possible to measure a length of an object.
Also, in the present invention, it is possible to measure a relative moving speed and a shape pattern of a moving object, when an observation point and the moving object are moving on a given track relative to the other. Also, it is possible to measure a length of a moving object, when the observation point is stationary.
Also, in the present invention, there is no need for placing line image recording apparatus (line scanning camera and the like) to surround the object, and therefore, the arrangement of the apparatuses is facilitated compared with conventional phototubes and the like. In contract to using the phototubes, image data of the object can be accumulated so that the object can be identified after the measurements.
Also, by using line image recording apparatus, it is possible to provide highspeed recording of a moving object at about 1000 times the speed of conventional video cameras, so that moving speed of a fast moving object can be determined. Unlike the case of using video cameras, many line image recording apparatuses can be positioned in parallel to enable speed measurements without being affected by problems related to the distance from the cameras.
Also, in the present invention, by increasing the number of line image recording apparatus to be used, the number of speed and length measurements that can be performed by the system increases according to the number of combination of the line image recording apparatuses to increase the accuracy of determination. Also, even if an object cannot be recognized from one image data due to adverse effects from noise and other factors, other image data can be processed for recognition so that pattern recognition accuracy can be improved.
Also, the present apparatus can be operated to record visible radiation passively so that an object can be recorded and its shape pattern recognized without being detected.